Free and Open Source Invoicing, Expenses & Time-Tracking
Free Invoice & Billing Software for Windows, Linux & Mac
Accounting system for smaller companies written in GnuCobol.
Accounting & Best Practice Business Administration System
JEE based Accounting web-application.
FreelancerBooks -Project Management for Freelancers and Agencies
its complete accounting system for small scale manufacturing companies
Mutasyon is a script can add customer, products, inventory or invoice
Captures time & expense by project and account; generates invoice
Software platform
Codeignitor PHP based system for Client management, Product management